Definición de blue ensign en inglés:

sustantivo

Until this time, vessels of the Commonwealth naval forces had flown the Naval blue ensign.

Eventually, common sense prevailed, and in about 1621 the first red ensign appeared, followed some years later by the white and blue ensigns to distinguish the three squadrons into which the fleet was now divided.

It was not until 1950, when the Commonwealth government decided to give a flag to every school to mark the jubilee of Federation, that it finally designated the blue ensign as the Australian national flag.